The present invention relates to digital integrated circuits (ICs). In particular, it relates to error detection in such circuits.
As microelectronics arts progress toward ever smaller devices, reliability is an increasing concern. One particular type failure mode in ICs is due to so called soft errors. There is no hardware damage, and the error is non repeatable, or traceable, hence the term “soft”. Soft errors may have many causes, but one unavoidable source of such errors is ionizing radiation in the form of alpha particles and cosmic rays.
If a soft error is detected, it may be mitigated in various ways, for instance by repeating the system's operation from some stored and presumably correct state. Soft errors in computation circuits may, however, result in undetected erroneous results. If these undetected errors are frequent enough, the reliability of the entire system may be suspect. In modern processors data from successive pipeline stages of computation is often stored, or latched, to provide inputs to a next pipeline stage. It is thus desirable to be able to detect soft errors that cause latches to change their state.